Programmed death-1 expression in liver transplant recipients as a prognostic indicator of cytomegalovirus disease

Immune-checkpoint expression in antigen-presenting cells (APCs) of cytomegaloviruses infection after transplantation: as a diagnostic biomarker

Cytomegalovirus (CMV), a member of the Herpesviridae family, mostly causes only slight feverish symptoms or can be asymptomatic in immunocompetent individuals. However, it is known to be particularly a significant cause of morbidity in immunocompromised patients, including transplant recipients, whose immune system has been weakened due to the consumption of immunosuppressor drugs. Therefore, the diagnosis of CMV infection after transplantation is crucial. New diagnostic methods for the quick detection of CMV have been developed as a result of understanding the clinical importance of invasive CMV. Antigen-presenting cells (APCs) and T cells are important components of the immune system and it may be possible to diagnose viral infections using immunological markers, such as lymphocytosis, cytotoxic T lymphocytes (CTL), and serum cytokine levels. Moreover, PD-1, CTLA 4, and TIGIT, which are expressed on certain T cells and antigen-presenting cells, are over-expressed during the infection. The assessment of CMV infection based on T cell and APC activity, and the expression of immunological checkpoints, can be helpful for the diagnosis of transplant patients at risk for CMV infection. In this review, we will investigate how immune checkpoints affect immune cells and how they impair organ transplantation after CMV infection.

Assessment of neutrophil subsets and immune checkpoint inhibitor expressions on T lymphocytes in liver transplantation: A preliminary study beyond the neutrophil-lymphocyte ratio

Background: Advanced stages of cirrhosis are characterized by the occurrence of progressive immune alterations known as CAID (Cirrhosis Associated Immune Dysfunction). In advanced cirrhosis, liver transplantation (LT) remains the only curative treatment. Sepsis, shares many similarities with decompensated cirrhosis in terms of immuno-inflammatory response. In both conditions, the neutrophil-lymphocyte ratio (NLR) is associated with poor outcomes. Based on alterations in sepsis, we hypothesized that we could observe in cirrhotic and LT patients more detailed neutrophil and lymphocyte phenotypes. To this end, along with leukocyte count, we assessed immature neutrophils, LOX-1⁺ MDSC and PD-1 and TIM-3 lymphocyte expressions in cirrhotic patients before transplantation in association with liver disease severity and during the first month after transplantation. Methods: We conducted a prospective monocentric study including cirrhotic patients registered on LT waiting-list. Blood samples were collected at enrolment before LT and for 1 month post-LT. In addition to NLR, we assessed by whole blood flow cytometry the absolute count of immature neutrophils and LOX-1⁺ MDSC as well as the expressions of immune checkpoint receptors PD-1 and TIM-3 on T lymphocytes. Results: We included 15 healthy volunteers (HV) and 28 patients. LT was performed for 13 patients. Pre-LT patients presented with a higher NLR compared to HV and NLR was associated with cirrhosis severity. Increased immature neutrophils and LOX-1⁺ MDSC counts were observed in the most severe patients. These alterations were mainly associated with acute decompensation of cirrhosis. PD-1 and TIM-3 expressions on T lymphocytes were not different between patients and HV. Post-LT immune alterations were dominated by a transitory but tremendous increase of NLR and immature neutrophils during the first days post-LT. Then, immune checkpoint receptors and LOX-1⁺ MDSC tended to be overexpressed by the second week after surgery. Conclusion: The present study showed that NLR, immature neutrophils and LOX-1⁺ MDSC counts along with T lymphocyte count and checkpoint inhibitor expression were altered in cirrhotic patients before and after LT. These data illustrate the potential interest of immune monitoring of cirrhotic patients in the context of LT in order to better define risk of sepsis. For this purpose, larger cohorts of patients are now necessary in order to move forward a more personalised care of LT patients.

Cytomegalovirus and other herpesviruses after hematopoietic cell and solid organ transplantation: From antiviral drugs to virus-specific T cells

Herpesviruses can either cause primary infection or may get reactivated after both hematopoietic cell and solid organ transplantations. In general, viral infections increase post-transplant morbidity and mortality. Prophylactic, preemptive, or therapeutically administered antiviral drugs may be associated with serious side effects and may induce viral resistance. Virus-specific T cells represent a valuable addition to antiviral treatment, with high rates of response and minimal side effects. Even low numbers of virus-specific T cells manufactured by direct selection methods can reconstitute virus-specific immunity after transplantation and control viral replication. Virus-specific T cells belong to the advanced therapy medicinal products, and their production is regulated by appropriate legislation; also, strict safety regulations are required to minimize their side effects.

Immune Modulation and Cytomegalovirus Reactivation in Sepsis-induced Immunosuppression: A Pilot Study

Introduction

Sepsis is a life-threatening condition caused due to dysregulated immune response to an infection and progressive immunosuppression. Reactivation of cytomegalovirus (CMV) occurs frequently in sepsis and is found associated with adverse outcomes. The study objective was to evaluate the association between incidence of CMV reactivation and immune alteration in sepsis-induced immunosuppression in patients with prolonged sepsis.

Patients and methods

Patients admitted to intensive care unit (ICU), with severe sepsis and CMV immunoglobulin G (IgG) seropositivity, were prospectively enrolled. Other manifest immune suppression causes were excluded. Samples were collected on enrolment and further once a week until day 21 or death/discharge. CMV viral load was quantified using qPCR. Lymphocyte subset analysis (CD3+, CD4+, CD8+, CD19+, CD16+/CD56+, and CD25+CD127− regulatory T cells), human leukocyte antigen-DR isotype (HLA-DR) expression on monocytes, programmed death-1 (PD-1) expression on T lymphocytes, and proinflammatory (interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and interferon-gamma (IFN-γ)), anti-inflammatory cytokines levels (IL-2, IL-4, and IL-10) were analyzed by flow cytometry as markers for immunosuppression.

Results

A total of 25 CMV IgG-positive patients and 11 healthy controls were included. CMV reactivation occurred in 20 patients. Patients with CMV reactivation had T-cell lymphopenia. PD-1 expression on CD4+ and CD8+ T cells was markedly elevated (p <0.02) in CMV-reactivated patients compared to nonreactivated patients. HLA-DR expression was significantly low on monocytes in all septic patients (p <0.01) compared to healthy controls. IL-6 levels showed elevation at day 7, whereas IL-10 was found to be significantly higher from day 0 in CMV-reactivated group.

Conclusion

Our study concluded that immune suppression markers and cytokine levels in patients with severe sepsis were found to be significantly associated with the incidence of CMV reactivation.

How to cite this article

Lambe G, Mansukhani D, Khodaiji S, Shetty A, Rodrigues C, Kapadia F. Immune Modulation and Cytomegalovirus Reactivation in Sepsis-induced Immunosuppression: A Pilot Study. Indian J Crit Care Med 2022;26(1):53–61.

Polymorphisms and Circulating Plasma Protein Levels of Immune Checkpoints (CTLA-4 and PD-1) Are Associated With Posner-Schlossman Syndrome in Southern Chinese

Cytotoxic T-lymphocyte associated protein 4 (CTLA-4) and programmed cell death 1 (PD-1) are well-known key immune checkpoints that play a crucial dampening effect on regulating T-cell homeostasis and self-tolerance. In this study, we aimed to evaluate the association between immune checkpoints (CTLA-4 and PD-1) and Posner-Schlossman syndrome (PSS) in a southern Chinese population. A total of 137 patients with PSS and 139 healthy controls from a southern Chinese population were recruited. Five single nucleotide polymorphisms (SNPs) of CTLA-4 (rs733618, rs4553808, rs5742909, rs231775, and rs3087243) and five SNPs of PD-1 (rs10204525, rs2227981, rs2227982, rs41386349, and rs36084323) were genotyped by SNaPshot technique. Soluble CTLA-4 (sCTLA-4) and soluble PD-1 (sPD-1) were determined by ELISA and antibody array assay, respectively. The frequencies of T allele at rs733618 and A allele at rs231775 of CTLA-4 were significantly higher in PSS patients than in healthy controls (corrected p (P_c) = 0.037; P_c = 0.044, respectively). The haplotype frequencies of CACGG haplotype (rs733618-rs4553808-rs5742909-rs231775-rs3087243) of CTLA-4 and TGAGC haplotype (rs10204525-rs2227981-rs2227982-rs41386349-rs36084323) of PD-1 in the PSS group was significantly lower than those in the control group (P_c = 0.015, p = 0.034, respectively). Circulating plasma levels of sCTLA-4 and sPD-1 in PSS patients were significantly higher than those in controls (all p < 0.001). The present study suggests that CTLA-4 and PD-1 genetic polymorphisms are associated with the susceptibility to PSS in a southern Chinese population. The upregulated circulating plasma protein levels of sCTLA-4 and sPD-1 might provide some hints regarding the dysfunction of immune checkpoints in PSS during the active status.

Fungal Infections Potentiated by Biologics

Biologic therapies including monoclonal antibodies, tyrosine kinase inhibitors, and other agents represent a notable expansion in the pharmacotherapy armamentarium in treatment of a variety of diseases. Many of these therapies possess direct or indirect immunosuppressive and immunomodulatory effects, which have been associated with bacterial, viral, and fungal opportunistic infections. Careful screening of baseline risk factors before initiation, targeted preventive measures, and vigilant monitoring while on active biologic therapy mitigate these risks as use of biologics becomes more commonplace. This review compiles reported evidence of fungal infections associated with these agents with a focus on the tumor necrosis factor-α inhibitor class.

Skewed T cell responses to Epstein-Barr virus in long-term asymptomatic kidney transplant recipients

Kidney transplant recipients (KTRs) abnormally replicate the Epstein Barr Virus (EBV). To better understand how long-term immunosuppression impacts the immune control of this EBV re-emergence, we systematically compared 10 clinically stable KTRs to 30 healthy controls (HCs). The EBV-specific T cell responses were determined in both groups by multiparameter flow cytometry with intra cellular cytokine staining (KTRs n = 10; HCs n = 15) and ELISpot-IFNγ assays (KTRs n = 7; HCs n = 7). The T/B/NK cell counts (KTRs n = 10; HCs n = 30) and the NK/T cell differentiation and activation phenotypes (KTRs n = 10; HCs n = 15/30) were also measured. We show that in KTRs, the Th1 effector CD4+ T cell responses against latent EBV proteins are weak (2/7 responders). Conversely, the frequencies total EBV-specific CD8+T cells are conserved in KTRs (n = 10) and span a wider range of EBNA-3A peptides (5/7responders) than in HCs (5/7responders). Those modifications of the EBV-specific T cell response were associated with a profound CD4+ T cell lymphopenia in KTRs compared to HCs, involving the naïve CD4+ T cell subset, and a persistent activation of highly-differentiated senescent CD8+ T cells. The proportion of total NK / CD8+ T cells expressing PD-1 was also increased in KTRs. Noteworthy, PD-1 expression on CD8+ T cells normalized with time after transplantation. In conclusion, we show modifications of the EBV-specific cellular immunity in long term transplant recipients. This may be the result of both persistent EBV antigenic stimulation and profound immunosuppression induced by anti-rejection treatments. These findings provide new insights into the immunopathology of EBV infection after renal transplantation.

Enhancement of Cytomegalovirus-Specific Cytokine Production after Modulation of the Costimulation in Kidney Transplant Patients

Kidney transplantation is the therapy of choice for patients with end stage renal disease. Due to immunosuppressive treatment, patients are at risk for opportunistic infections. Cytomegalovirus (CMV) reactivation is highly relevant in kidney transplant recipients because it occurs—depending on the serological constellation of the donor and recipient—in more than half of the patients and influences patient outcome. Patients with CMV reactivation show decreased allograft and overall survival. Previous studies could demonstrate that transplant patients often show weak CMV-specific immunity. Besides immunosuppressive treatment, additional mechanisms may reduce CMV-specific immunocompetence such as enhanced negative costimulation. Hence, the aim of this study was to investigate if the function of CMV-specific cells of kidney transplant recipients could be restored by a modulation of costimulatory molecules. To address this question, lymphocytes of kidney transplant patients were stimulated with CMV-specific antigens and incubated with programmed death-ligand 1 (PD-L1), programmed cell death protein 1 (PD-1), or B- and T-lymphocyte attenuator (BTLA) antibodies. Afterwards, the IFN-γ, IL-21, and IL-17A production was measured by the ELISpot assay. It could be shown that a blockade of the ligand PD-L1 resulted in an increased CMV-specific IFN-γ, IL-21, and IL-17A secretion. The blockade of the receptor PD-1 distinctly enhanced the production of IL-21. BTLA antibodies, however, led only to a marginal increase of CMV-specific IFN-γ and of IL-21 production. Experiments in healthy controls could confirm the results of the kidney transplant recipients. Furthermore, they could demonstrate that treatment with the immunosuppressive drug tacrolimus resulted in decreased CMV-specific IFN-γ and of IL-21 production. Thus, our study could show for the first time that the blockade of the PD-L1/PD-1 pathway also modulates CMV-specific Th21 and Th17 cell function in kidney transplant recipients. Further studies are mandatory to clarify the role of Th21 and Th17 cells in CMV control of these patients.

The Third International Consensus Guidelines on the Management of Cytomegalovirus in Solid-organ Transplantation

Despite recent advances, cytomegalovirus (CMV) infections remain one of the most common complications affecting solid organ transplant recipients, conveying higher risks of complications, graft loss, morbidity, and mortality. Research in the field and development of prior consensus guidelines supported by The Transplantation Society has allowed a more standardized approach to CMV management. An international multidisciplinary panel of experts was convened to expand and revise evidence and expert opinion-based consensus guidelines on CMV management including prevention, treatment, diagnostics, immunology, drug resistance, and pediatric issues. Highlights include advances in molecular and immunologic diagnostics, improved understanding of diagnostic thresholds, optimized methods of prevention, advances in the use of novel antiviral therapies and certain immunosuppressive agents, and more savvy approaches to treatment resistant/refractory disease. The following report summarizes the updated recommendations.

Rapid Acquisition of Cytomegalovirus-Specific T Cells with a Differentiated Phenotype, in Nonviremic Hematopoietic Stem Transplant Recipients Vaccinated with CMVPepVax

Early cytomegalovirus (CMV) reactivation remains a significant cause of morbidity and mortality in allogeneic hematopoietic cell transplant (HCT) recipients. CMVPepVax is an investigational peptide vaccine designed to control CMV infection in HCT recipients seropositive for CMV by stimulating the expansion of T cell subsets that target the CMV tegument protein pp65. In a randomized Phase Ib pilot trial (ClinicalTrials.gov NCT01588015), two injections of CMVPepVax (at days 28 and 56 post-HCT) demonstrated safety, immunogenicity, increased relapse-free survival, and reduced CMV reactivation and use of antivirals. In the present study, we assessed the phenotypes and time courses of the pp65-specific CD8 T cell subsets that expanded in response to CMVPepVax vaccination. The functionality and antiviral role of CMV-specific T cells have been linked to immune reconstitution profiles characterized predominantly by differentiated effector memory T (TEM) subsets that have lost membrane expression of the costimulatory molecule CD28 and often reexpress the RA isoform of CD45 (TEMRA). Major histocompatibility complex class I pp65_495-503 multimers, as well as CD28 and CD45 memory markers, were used to detect immune reconstitution in blood specimens from HCT recipients enrolled in the Phase Ib clinical trial. Specimens from the 10 (out of 18) vaccinated patients who had adequate (≥.2%) multimer binding to allow for memory analysis showed highly differentiated TEM and TEMRA phenotypes for pp65_495-503-specific CD8 T cells during the first 100days post-transplantation. In particular, by day 70, during the period of highest risk for CMV reactivation, combined TEM and TEMRA phenotypes constituted a median of 90% of pp65_495-503-specific CD8 T cells in these vaccinated patients. CMV viremia was not detectable in the patients who received CMVPepVax, although their pp65_495-503-specific CD8 T cell profiles were strikingly similar to those observed in viremic patients who did not receive the vaccine. Collectively, our findings indicate that in the absence of clinically relevant viremia, CMVPepVax reconstituted significant levels of differentiated pp65_495-503-specific CD8 TEMs early post-HCT. Our data indicate that the rapid reconstitution of CMV-specific T cells with marked levels of effector phenotypes may have been key to the favorable outcomes of the CMVPepVax clinical trial.

New Developments in the Management of Cytomegalovirus Infection After Transplantation

Cytomegalovirus (CMV) continues to be one of the most important pathogens that universally affect solid organ and allogeneic hematopoietic stem cell transplant recipients. Lack of effective CMV-specific immunity is the common factor that predisposes to the risk of CMV reactivation and clinical disease after transplantation. Antiviral drugs are the cornerstone for prevention and treatment of CMV infection and disease. Over the years, the CMV DNA polymerase inhibitor, ganciclovir (and valganciclovir), have served as the backbone for management, while foscarnet and cidofovir are reserved for the management of CMV infection that is refractory or resistant to ganciclovir treatment. In this review, we highlight the role of the newly approved drug, letermovir, a viral terminase inhibitor, for CMV prevention after allogeneic hematopoietic stem cell transplantation. Advances in immunologic monitoring may allow for an individualized approach to management of CMV after transplantation. Specifically, the potential role of CMV-specific T-cell measurements in guiding the need for the treatment of asymptomatic CMV infection and the duration of treatment of CMV disease is discussed. The role of adoptive immunotherapy, using ex vivo-generated CMV-specific T cells, is highlighted. This article provides a review of novel drugs, tests, and strategies in optimizing our current approaches to prevention and treatment of CMV in transplant recipients.

Impaired polyfunctionality of CD8+ T cells in severe sepsis patients with human cytomegalovirus reactivation

Human cytomegalovirus (HCMV) establishes a lifelong chronic latent infection and often reactivates in immunocompromised patients. In addition, HCMV reactivates in patients with sepsis or other critical illnesses, particularly in patients with poor prognoses. However, the immunological characteristics of sepsis patients with HCMV reactivation have not been elucidated. In the present study, we examined T-cell responses in severe sepsis patients with and without HCMV reactivation. First, HCMV pp65-specific T-cell functions were assessed by intracellular cytokine staining (ICS) for IFN-γ, TNF-α, and MIP-1β and by CD107a staining. We analyzed the ICS data for each function individually and found no difference between the patient groups. However, the relative frequency of polyfunctional CD8⁺ T cells was significantly decreased in sepsis patients with HCMV reactivation. Next, we examined programmed cell death protein 1 (PD-1) expression. It was significantly increased in the CD8⁺ T-cell population in severe sepsis patients with HCMV reactivation, indicating CD8⁺ T-cell exhaustion. Interestingly, the frequency of PD-1⁺ cells in the CD8⁺ T-cell population was inversely correlated with the relative frequency of polyfunctional CD8⁺ T cells. Herein, we demonstrate that HCMV reactivation in severe sepsis patients is associated with PD-1 expression and impaired polyfunctionality of CD8⁺ T cells.

Polymorphism in programmed cell death 1 gene is strongly associated with lung and kidney allograft survival in recipients from CMV-positive donors

BACKGROUND

Cytomegalovirus (CMV) has a role in chronic rejection and graft loss in kidney transplant (KTx) and lung transplant (LTx) recipients. In addition, donor CMV seropositivity is an independent risk factor for renal graft loss. The anti-CMV response might modulate this risk. Expression of programmed cell death 1 (PD-1), a receptor involved in viral-specific T-cell exhaustion, is influenced by a single nucleotide polymorphism called PD-1.3 (wild-type allele G, variant allele A).

METHODS

We performed a retrospective study to assess the impact of PD-1.3 on graft outcome in donor CMV seropositive (D+) and donor CMV seronegative (D-) KTx and LTx. We also performed a case-control study to evaluate the anti-CMVpp65 response according to genotype.

RESULTS

PD-1.3 was determined in 1,119 KTx and 181 LTx. In 481 D+ KTx, A allele carriers (24%) experienced significantly less graft failure compared with GG carriers (p = 0.001). Multivariate analysis showed that this association was independent of donor and recipient age, acute rejection episodes, and number of human leukocyte antigen mismatches (hazard ratio, 0.381; 95% confidence interval, 0.209-0.696; p = 0.002). Analysis in 85 D+ LTx showed similar results: A allele carriers had better survival (hazard ratio, 0.302; 95% confidence interval, 0.128-0.716; p = 0.006) and greater 6-month forced expiratory volume (71% ± 17% vs 54% ± 16%, p = 0.001). In D- recipients, PD-1.3 did not affect KTx or LTx outcome. Finally, AA recipients had a stronger anti-CMVpp65 T-cell response than matched GG recipients (p = 0.003).

CONCLUSIONS

The A variant allele in PD-1.3 single nucleotide polymorphism improved graft survival in kidney and lung transplant recipients receiving grafts from CMV-positive donors.

CD28 positive, cytomegalovirus specific cytotoxic T lymphocytes as a novel biomarker associated with cytomegalovirus viremia in kidney allorecipients

BACKGROUND

CMV infection remains major complication after kidney transplantation, thus diagnostics tools that would improve identification of individuals at risk of development of CMV - related complications are useful. For this reason, searching for proper immunological biomarkers candidates gives hope to individualize antiviral therapy and minimize side effects of antiviral drugs.

OBJECTIVES

The purpose of this research was to assess immune assays that can be used to predict the likelihood of CMV viremia after kidney allotransplantation.

STUDY DESIGN

In the study, immunological markers of CMV viremia were assessed in 52 kidney transplant recipients during two years lasting follow-up. Immunological markers associated with viral infection, like lymphocytosis, cytotoxic T lymphocytes (CTL) and serum cytokines levels were compared with less common immunological assays, like activated T lymphocytes, CMV-specific CTL stratified according to naïve/memory phenotype. The test to assess expression of CD28 antigen on CTL, as a possible additional marker of CMV-specificity, was developed.

RESULTS

CD28-positive CMV-specific CTL have been found the most useful marker for CMV viremia prediction. Tested value of 3 cells/μl was found to be most suitable for CMV activation assessment with acceptable sensitivity and specificity.

DISCUSSION

This preliminary report suggests that CD28-positive CMV-specific CTL could be put at the first line, as possible novel marker associated with CMV viremia development.

The "ABC" of Virus-Specific T Cell Immunity in Solid Organ Transplantation

Transplant patients are at increased risk of viral complications due to impaired control of viral replication, resulting from HLA mismatching between graft and host and the immunosuppression needed to avert alloimmune reactions. In the past decade, quantitative viral load measurements have become widely available to identify patients at risk and to inform treatment decisions with respect to immunosuppressive drugs and antiviral therapies. Because viral loads are viewed as the result of viral replication and virus-specific immune control, virus-specific T cell monitoring has been explored to optimize management of adenovirus, BK polyomavirus and cytomegalovirus ("ABC") in transplant patients. Although most studies are descriptive using different technologies, the overall results show that the quantity and quality of virus-specific T cells inversely correlate with viral replication, whereby strong cellular immune responses are associated with containment of viral replication. The key obstacles to the introduction of assays for virus-specific T cells into clinical practice is the definition of reliable cutoffs for clinical decision making, the poor negative predictive value of some assays, and the absence of interventional trials justifying changes of antiviral treatment or immunosuppression. More clinical research is needed using optimized assays and targets before standardization and commutability can be envisaged as achieved for viral load testing.

Plasma IL-10 Levels to Guide Antiviral Prophylaxis Prevention of Late-Onset Cytomegalovirus Disease, in High Risk Solid Kidney and Liver Transplant Recipients

BACKGROUND

Immune measurements that distinguish solid organ transplantation (SOT) recipients who control cytomegalovirus (CMV) infection from those who progress to CMV-disease (CMV-dz) may be clinically useful in guiding tailored prevention strategies. We previously reported that elevated plasma levels of the immune-modulator IL-10 are associated with late CMV-dz. Here we evaluate whether IL-10 levels measured soon after prophylaxis discontinuation are predictive of CMV-dz risk.

METHODS

Plasma IL-10 levels were quantitatively measured by ELISA kit in 40 D/R SOT patients. All 40 D/R high-risk patients were prospectively followed for at least 12 months post-SOT: 13 subjects developed CMV-dz, all within 6 months of prophylaxis discontinuation.

RESULTS

IL-10 was detectable at the first post-prophylaxis measurement for 11 of 13 subjects who developed CMV-dz. In contrast, IL-10 was detectable in only 6 of 27 CMV asymptomatic patients. Monitoring IL-10 plasma levels within 1 month prophylaxis suspension appeared to have clinically useful level of 85% sensitivity and 78% specificity.

CONCLUSIONS

The exact role of IL-10 with its multiple immunoregulatory effects during CMV infection is not clear. Moreover, IL-10 production can be influenced by pathological and infectious contexts, and/or anti-rejection immunosuppressant therapy. Despite mechanisms of IL-10 dysregulation may substantially differ among SOT patients, our findings suggest that measurable plasma IL-10 soon after prophylaxis discontinuation may be an adequate indicator of subsequent CMV-dz. If a similar prognostic performance is confirmed in a larger D/R cohort, IL-10 plasma levels could be used to guide the length of prophylaxis, providing a clinically useful means to reduce the incidence of CMV-dz in high risk patients.

[Immunomonitoring for cytomegalovirus infection in kidney transplantation: Development and prospects]

Cytomegalovirus infection in kidney transplantation is associated with increased morbidity and mortality through direct and indirect effects. International guidelines had been recently updated, focusing on diagnostic, prevention strategies and curative treatment. Cytomegalovirus-specific immune response plays also an important function in controlling the virus. Here, we propose to present the different components of this specific immune response and the advantages of immune monitoring for patient's management: identification of patients who require a treatment, adaptation of curative treatment length, guidance for resistance genotypic testing.

Surveillance of γδ T Cells Predicts Cytomegalovirus Infection Resolution in Kidney Transplants

Cytomegalovirus (CMV) infection in solid-organ transplantation is associated with increased morbidity and mortality, particularly if a CMV mutant strain with antiviral resistance emerges. Monitoring CMV-specific T cell response could provide relevant information for patient care. We and others have shown the involvement of Vδ2(neg) γδ T cells in controlling CMV infection. Here, we assessed if Vδ2(neg) γδ T cell kinetics in peripheral blood predict CMV infection resolution and emergence of a mutant strain in high-risk recipients of kidney transplants, including 168 seronegative recipients receiving organs from seropositive donors (D+R-) and 104 seropositive recipients receiving antithymocyte globulins (R+/ATG). Vδ2(neg) γδ T cell percentages were serially determined in patients grafted between 2003 and 2011. The growing phase of Vδ2(neg) γδ T cells was monitored in each infected patient, and the expansion rate during this phase was estimated individually by a linear mixed model. A Vδ2(neg) γδ T cell expansion rate of ˃0.06% per day predicted the growing phase. The time after infection at which an expansion rate of 0.06% per day occurred was correlated with the resolution of CMV DNAemia (r=0.91; P<0.001). At 49 days of antiviral treatment, Vδ2(neg) γδ T cell expansion onset was associated with recovery, whereas absence of expansion was associated with recurrent disease and DNAemia. The appearance of antiviral-resistant mutant CMV strains was associated with delayed Vδ2(neg) γδ T cell expansion (P<0.001). In conclusion, longitudinal surveillance of Vδ2(neg) γδ T cells in recipients of kidney transplants may predict CMV infection resolution and antiviral drug resistance.

Effects of donor/recipient human leukocyte antigen mismatch on human cytomegalovirus replication following liver transplantation

BACKGROUND

Natural immunity against cytomegalovirus (CMV) can control virus replication after solid organ transplantation; however, it is not known which components of the adaptive immune system mediate this protection. We investigated whether this protection requires human leukocyte antigen (HLA) matching between donor and recipient by exploiting the fact that, unlike transplantation of other solid organs, liver transplantation does not require HLA matching, but some donor and recipient pairs may nevertheless be matched by chance.

METHODS

To further investigate this immune control, we determined whether chance HLA matching between donor (D) and recipient (R) in liver transplants affected a range of viral replication parameters.

RESULTS

In total, 274 liver transplant recipients were stratified according to matches at the HLA A, HLA B, and HLA DR loci. The incidence of CMV viremia, kinetics of replication, and peak viral load were similar between the HLA matched and mismatched patients in the D+/R+ and D-/R+ transplant groups. D+/R- transplants with 1 or 2 mismatches at the HLA DR locus had a higher incidence of CMV viremia >3000 genomes/mL blood compared to patients matched at this locus (78% vs. 17%; P = 0.01). Evidence was seen that matching at the HLA A locus had a small effect on peak viral loads in D+/R- patients, with median peak loads of 3540 and 14,706 genomes/mL in the 0 and combined (1 and 2) mismatch groups, respectively (P = 0.03).

CONCLUSION

Overall, our data indicate that, in the setting of liver transplantation, prevention of CMV infection and control of CMV replication by adaptive immunity is minimally influenced by HLA matching of the donor and recipient. Our data raise questions about immune control of CMV in the liver and also about the cells in which the virus is amplified to give rise to CMV viremia.

Management of cytomegalovirus infection and disease in liver transplant recipients

Cytomegalovirus (CMV) is one of the most common viral pathogens causing clinical disease in liver transplant recipients, and contributing to substantial morbidity and occasional mortality. CMV causes febrile illness often accompanied by bone marrow suppression, and in some cases, invades tissues including the transplanted liver allograft. In addition, CMV has been significantly associated with an increased predisposition to acute and chronic allograft rejection, accelerated hepatitis C recurrence, and other opportunistic infections, as well as reduced overall patient and allograft survival. To negate the adverse effects of CMV infection on transplant outcome, its prevention, whether through antiviral prophylaxis or preemptive therapy, is an essential component to the management of liver transplant recipients. Two recently updated guidelines have suggested that antiviral prophylaxis or preemptive therapy are similarly effective in preventing CMV disease in modest-risk CMV-seropositive liver transplant recipients, while antiviral prophylaxis is the preferred strategy over preemptive therapy for the prevention of CMV disease in high-risk recipients [CMV-seronegative recipients of liver allografts from CMV-seropositive donors (D+/R-)]. However, antiviral prophylaxis has only delayed the onset of CMV disease in many CMV D+/R- liver transplant recipients, and such occurrence of late-onset CMV disease was significantly associated with increased all-cause and infection-related mortality after liver transplantation. Therefore, a search for better strategies for prevention, such as prolonged duration of antiviral prophylaxis, a hybrid approach (antiviral prophylaxis followed by preemptive therapy), or the use of immunologic measures to guide antiviral prophylaxis has been suggested to prevent late-onset CMV disease. The standard treatment of CMV disease consists of intravenous ganciclovir or oral valganciclovir, and if feasible, reduction in pharmacologic immunosuppression. In one clinical trial, oral valganciclovir was as effective as intravenous ganciclovir for the treatment of mild to moderate CMV disease in solid organ (including liver) transplant recipients. The aim of this article is to provide a state-of-the art review of the epidemiology, diagnosis, prevention, and treatment of CMV infection and disease after liver transplantation.

Clinical immune-monitoring strategies for predicting infection risk in solid organ transplantation

Infectious complications remain a leading cause of morbidity and mortality after solid organ transplantation (SOT), and largely depend on the net state of immunosuppression achieved with current regimens. Cytomegalovirus (CMV) is a major opportunistic viral pathogen in this setting. The application of strategies of immunological monitoring in SOT recipients would allow tailoring of immunosuppression and prophylaxis practices according to the individual's actual risk of infection. Immune monitoring may be pathogen-specific or nonspecific. Nonspecific immune monitoring may rely on either the quantification of peripheral blood biomarkers that reflect the status of a given arm of the immune response (serum immunoglobulins and complement factors, lymphocyte sub-populations, soluble form of CD30), or on the functional assessment of T-cell responsiveness (release of intracellular adenosine triphosphate following a mitogenic stimulus). In addition, various methods are currently available for monitoring pathogen-specific responses, such as CMV-specific T-cell-mediated immune response, based on interferon-γ release assays, intracellular cytokine staining or main histocompatibility complex-tetramer technology. This review summarizes the clinical evidence to date supporting the use of these approaches to the post-transplant immune status, as well as their potential limitations. Intervention studies based on validated strategies for immune monitoring still need to be performed.

PD-1 analysis on CD28(-) CD27(-) CD4 T cells allows stimulation-independent assessment of CMV viremic episodes in transplant recipients

Expression of the inhibitory receptor programmed death 1 (PD-1) on cytomegalovirus (CMV)-specific CD4 T cells defines a phenotype associated with CMV viremia in transplant recipients. Moreover, CD28(-) CD27(-) double negativity is known as a typical phenotype of CMV-specific CD4 T cells. Therefore, the co-expression of inhibitory receptors on CD28(-) CD27(-) CD4 T cells was assessed as a rapid, stimulation-independent parameter for monitoring CMV complications after transplantation. Ninety-three controls, 67 hemodialysis patients and 81 renal transplant recipients were recruited in a cross-sectional and longitudinal manner. CMV-specific CD4 T cell levels quantified after stimulation were compared to levels of CD28(-) CD27(-) CD4 T cells. PD-1 and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) expression on CD28(-) CD27(-) CD4 T cells were related to viremia. A percentage of ≥0.44% CD28(-) CD27(-) CD4 T cells defined CMV seropositivity (93.3% sensitivity, 97.1% specificity), and their frequencies correlated strongly with CMV-specific CD4 T cell levels after stimulation (r = 0.73, p < 0.0001). Highest PD-1 expression levels on CD28(-) CD27(-) CD4 T cells were observed in patients with primary CMV viremia and reactivation (p < 0.0001), whereas CTLA-4 expression was only elevated during primary CMV viremia (p < 0.05). Longitudinal analysis showed a significant increase in PD-1 expression in relation to viremia (p < 0.001), whereas changes in nonviremic patients were nonsignificant. In conclusion, increased PD-1 expression on CD28(-) CD27(-) CD4 T cells correlates with CMV viremia in transplant recipients and may serve as a specific, stimulation-independent parameter to guide duration of antiviral therapy.

Increased levels of PD-1 expression on CD8 T cells in patients post-renal transplant irrespective of chronic high EBV viral load

Studies have identified solid organ transplant recipients who remain asymptomatic despite maintaining CHL. Factors which determine the CHL state remain poorly understood but are likely to involve immunological control of the viral infection. We monitored expression of PD-1, a marker of T-cell exhaustion and viral persistence, on CD8 T cells in patients who resolved EBV infection as determined by undetectable EBV DNA (REI) and CHL patients. PD-1 expression on CD8 T cells was increased in the first year post-transplant irrespective of EBV outcome, and most CD8 T cells continued to express PD-1 for up to three yr post-transplant. Although all patient groups showed similar frequencies of EBV-specific CD8+ T cells, PD-1 expression on these cells increased in the post-transplant groups compared with the pretransplant patients. Functional studies of EBV-specific CD8+ T cells stimulated with BZLF or LMP2 peptide pools revealed monofunctional IFN-γ responses. Our results indicate that PD-1 expression on CD8 T cells post-transplant may result from factors other than antigenic stimulation.

Association of the costimulatory molecule gene polymorphisms and active cytomegalovirus infection in hematopoietic stem cell transplant patients

Determinative associations may exist between costimulatory molecule gene polymorphisms with a variety of post hematopoietic stem cell transplantation (HSCT) viral related clinical outcomes especially acute graft versus host disease (aGVHD). Therefore in this study the associations between costimulatory molecule gene polymorphisms including: cytotoxic T-lymphocyte antigen-4 (CTLA4), programmed cell death-1 (PD-1), inducible T cell costimulator (ICOS), and cluster differentiation 28 (CD28) with active cytomegalovirus (CMV) infection were evaluated in HSCT patients. The 72 allogeneic HSCT patients with and without aGVHD were enrolled in this cross sectional study between years: 2004-2011. The single nucleotide polymorphisms in loci of the costimulatory molecules including: CTLA4 gene (-318 C/T, 1722 T/C, 1661 A/G, +49 A/G), PD-1 gene (PD-1.3 A/G, PD-1.9 C/T), ICOS gene (1720 C/T), and CD28 gene (+17 C/T) were analyzed in studied HSCT patients by PCR-RFLP methods. The active CMV infection was evaluated in fresh EDTA-treated blood samples of each allogeneic HSCT patients by CMV antigenemia kit according to manufacturer's instruction. Active CMV infection was found in 11 of 72 (15.27 %) of allogeneic HSCT patients. The T allele and TT genotype of the CD28 +17 C/T were significantly higher frequency in active CMV infected allogeneic HSCT patients experienced aGVHD. The G allele and GG genotype of the CTLA4 -1661 A/G were significantly higher frequent in active CMV infected allogeneic HSCT patients experienced low grade of aGVHD. Finally, finding of significant associations between CD28 +17 C/T and CTLA4 -1661 A/G genotypes with CMV active infection in allogeneic HSCT patients experienced aGVHD emphasize on the importance of the genetic pattern of costimulatory genes in outcomes of active CMV infection in HSCT patients needs completed studies.

Association of the costimulatory molecule gene polymorphisms and active cytomegalovirus infection in hematopoietic stem cell transplant patients

Determinative associations may exist between costimulatory molecule gene polymorphisms with a variety of post hematopoietic stem cell transplantation (HSCT) viral related clinical outcomes especially acute graft versus host disease (aGVHD). Therefore in this study the associations between costimulatory molecule gene polymorphisms including: cytotoxic T-lymphocyte antigen-4 (CTLA4), programmed cell death-1 (PD-1), inducible T cell costimulator (ICOS), and cluster differentiation 28 (CD28) with active cytomegalovirus (CMV) infection were evaluated in HSCT patients. The 72 allogeneic HSCT patients with and without aGVHD were enrolled in this cross sectional study between years: 2004-2011. The single nucleotide polymorphisms in loci of the costimulatory molecules including: CTLA4 gene (-318 C/T, 1722 T/C, 1661 A/G, +49 A/G), PD-1 gene (PD-1.3 A/G, PD-1.9 C/T), ICOS gene (1720 C/T), and CD28 gene (+17 C/T) were analyzed in studied HSCT patients by PCR-RFLP methods. The active CMV infection was evaluated in fresh EDTA-treated blood samples of each allogeneic HSCT patients by CMV antigenemia kit according to manufacturer's instruction. Active CMV infection was found in 11 of 72 (15.27 %) of allogeneic HSCT patients. The T allele and TT genotype of the CD28 +17 C/T were significantly higher frequency in active CMV infected allogeneic HSCT patients experienced aGVHD. The G allele and GG genotype of the CTLA4 -1661 A/G were significantly higher frequent in active CMV infected allogeneic HSCT patients experienced low grade of aGVHD. Finally, finding of significant associations between CD28 +17 C/T and CTLA4 -1661 A/G genotypes with CMV active infection in allogeneic HSCT patients experienced aGVHD emphasize on the importance of the genetic pattern of costimulatory genes in outcomes of active CMV infection in HSCT patients needs completed studies.

Updated international consensus guidelines on the management of cytomegalovirus in solid-organ transplantation

Cytomegalovirus (CMV) continues to be one of the most common infections after solid-organ transplantation, resulting in significant morbidity, graft loss, and adverse outcomes. Management of CMV varies considerably among transplant centers but has been become more standardized by publication of consensus guidelines by the Infectious Diseases Section of The Transplantation Society. An international panel of experts was reconvened in October 2012 to revise and expand evidence and expert opinion-based consensus guidelines on CMV management, including diagnostics, immunology, prevention, treatment, drug resistance, and pediatric issues. The following report summarizes the recommendations.

Immune regulation of human herpesviruses and its implications for human transplantation

Human herpesviruses including cytomegalovirus, Epstein-Barr virus, HHV6, HHV7, HHV8, Herpes simplex virus (HSV)-1 and HSV-2 and varicella zoster virus (VZV) have developed an intricate relationship with the human immune system. This is characterized by the interplay between viral immune evasion mechanisms that promote the establishment of a lifelong persistent infection and the induction of a broad humoral and cellular immune response, which prevents the establishment of viral disease. Understanding the immune parameters that control herpesvirus infection, and the strategies the viruses use to evade immune recognition, has been critical in understanding why immunological dysfunction in transplant patients can lead to disease, and in the development of immunological strategies to prevent and control herpesvirus associated diseases.

Blockade of programmed death receptor-1 signaling restores expression of mostly proinflammatory cytokines in anergic cytomegalovirus-specific T cells

BACKGROUND

Programmed death receptor-1 (PD-1) compromises cytomegalovirus (CMV)-specific T-cell responses and has been linked to CMV viremia after transplantation. An impaired functional and proliferative capacity of PD-1-positive CMV-specific T cells may be reversed by the antibody-mediated blockade of PD-1 signaling. However, knowledge is limited on changes in "cytokinome" expression profiles associated with reversal of functional exhaustion.

METHODS

The "cytokinome" was analyzed by 27-plex Luminex technology comparing renal transplant recipients with low (n = 5) and high (n = 5) PD-1 expression on CMV-specific T cells. The effect of blocking PD-1 by PD-ligand (PD-L) antibodies on restoration of cytokine expression was examined.

RESULTS

CMV-specific cytokine release and proliferation was lower in patients with high PD-1 expression on CMV-specific T cells. Antibody-mediated blockade of PD-L in CMV-stimulated samples restored expression levels of interleukin (IL)-1β, IL-2, IL-6, IL-9, IL-10, granulocyte colony-stimulating factor, interferon-γ, macrophage inflammatory protein-1α, and tumor necrosis factor-α. By contrast, no profound effect was observed for controls or patients with low PD-1 expression, or in staphylococcal enterotoxin B-stimulated cells.

CONCLUSION

Taken together, this pilot study provides evidence that a high PD-1 expression on CMV-specific T cells actively impairs proliferation and "cytokinome" responses in an antigen-specific manner. Importantly, blockade of PD-L restores CMV-specific T-cell proliferation and expression of a panel of different proinflammatory and/or type 1 cytokines, suggesting a common but as yet unknown regulatory principle. We conclude that PD-1 exhaustion is reversible and potentially amenable to therapeutic ex vivo and possibly in vivo manipulation. However, detailed knowledge of the differential effects on the "cytokinome" will be necessary to increase the safety and the efficacy of such manipulations.

Cytomegalovirus replication kinetics in solid organ transplant recipients managed by preemptive therapy

After allotransplantation, cytomegalovirus (CMV) may be transmitted from the donor organ, giving rise to primary infection in a CMV negative recipient or reinfection in one who is CMV positive. In addition, latent CMV may reactivate in a CMV positive recipient. In this study, serial blood samples from 689 kidney or liver transplant recipients were tested for CMV DNA by quantitative PCR. CMV was managed using preemptive antiviral therapy and no patient received antiviral prophylaxis. Dynamic and quantitative measures of viremia and treatment were assessed. Median peak viral load, duration of viremia and duration of treatment were highest during primary infection, followed by reinfection then reactivation. In patients who experienced a second episode of viremia, the viral replication rate was significantly slower than in the first episode. Our data provide a clear demonstration of the immune control of CMV in immunosuppressed patients and emphasize the effectiveness of the preemptive approach for prevention of CMV syndrome and end organ disease. Overall, our findings provide quantitative biomarkers which can be used in pharmacodynamic assessments of the ability of novel CMV vaccines or antiviral drugs to reduce or even interrupt such transmission.

[Immunological monitoring strategies for cytomegalovirus infection. Immune-based therapies]

T-cell response to cytomegalovirus (CMV) is essential in the control of viral replication. Quantification of functional CD4(+) and CD8(+) T lymphocytes against certain CMV-antigen specificities through flow cytometry, ELISPOT or the QuantiFERON-CMV kit allows fairly accurate estimation of the risk of active infection and CMV disease in solid organ transplantation (SOT). Combined virological and immunological monitoring of CMV infection could allow antiviral treatments to be individually tailored and optimized in SOT, although clinical experience is currently lacking. The adoptive transfer of CMV-specific T cells before selection with multimer HLA peptides or after activation and expansion ex vivo could be an effective therapeutic alternative in the management of active infection or organic CMV disease refractory to antiviral therapy. Several CMV vaccines have been developed, which have been shown to be safe and immunogenic in preclinical and Phase I clinical trials. However, to date, none of these vaccines has been evaluated in Phase III clinical trials and consequently none has been approved for clinical use.

CD28 family and chronic rejection: "to belatacept...And beyond!"

Kidneys are one of the most frequently transplanted human organs. Immunosuppressive agents may prevent or reverse most acute rejection episodes; however, the graft may still succumb to chronic rejection. The immunological response involved in the chronic rejection process depends on both innate and adaptive immune response. T lymphocytes have a pivotal role in chronic rejection in adaptive immune response. Meanwhile, we aim to present a general overview on the state-of-the-art knowledge of the strategies used for manipulating the lymphocyte activation mechanisms involved in allografts, with emphasis on T-lymphocyte costimulatory and coinhibitory molecules of the B7-CD28 superfamily. A deeper understanding of the structure and function of these molecules improves both the knowledge of the immune system itself and their potential action as rejection inducers or tolerance promoters. In this context, the central role played by CD28 family, especially the relationship between CD28 and CTLA-4, becomes an interesting target for the development of immune-based therapies aiming to increase the survival rate of allografts and to decrease autoimmune phenomena. Good results obtained by the recent development of abatacept and belatacept with potential clinical use aroused better expectations concerning the outcome of transplanted patients.

Differential decay kinetics of human cytomegalovirus glycoprotein B genotypes following antiviral chemotherapy

Background

The impact of different cytomegalovirus (HCMV) glycoprotein B (gB) genotypes on pathogenesis remains controversial.

Objectives

To investigate the effect of gB genotypes either as single infections or as part of multiple infections on the early kinetics of response to ganciclovir therapy.

Methods

Patients (n = 239) enrolled in a study of intravenous ganciclovir or valganciclovir for the treatment of HCMV disease were analysed by a gB genotype specific PCR to quantify the amount of each gB genotype present at initiation of therapy (baseline, day 0) and at days 3, 7, 14 and 21 post therapy.

Results and conclusions

In all gB groups (individual gB genotype infections and mixed genotype infections) there was a biphasic decline in viral load after therapy. The first phase half life (days 0–3) was ≤1 day and was followed over the next 18 days by a slower second phase decline with half lives ranging from 3.4 to 4.4 days. The 1st phase rapid decline in viral load was dependent upon gB genotype whereas the ultimate viral load reduction at day 21 was relatively insensitive to gB genotype. A strong correlation between 1st phase decline and extent of viral load reduction at day 21 was observed (r = 0.37; p = 0.002). These data imply that early reductions in HCMV load after therapy may be useful in predicting the duration of drug therapy needed to control HCMV replication.

The immune response to human CMV

This review will summarize and interpret recent literature regarding the human CMV immune response, which is among the strongest measured and is the focus of attention for numerous research groups. CMV is a highly prevalent, globally occurring infection that rarely elicits disease in healthy immunocompetent hosts. The human immune system is unable to clear CMV infection and latency, but mounts a spirited immune-defense targeting multiple immune-evasion genes encoded by this dsDNA β-herpes virus. Additionally, the magnitude of cellular immune response devoted to CMV may cause premature immune senescence, and the high frequencies of cytolytic T cells may aggravate vascular pathologies. However, uncontrolled CMV viremia and life-threatening symptoms, which occur readily after immunosuppression and in the immature host, clearly indicate the essential role of immunity in maintaining asymptomatic co-existence with CMV. Approaches for harnessing the host immune response to CMV are needed to reduce the burden of CMV complications in immunocompromised individuals.

Dissecting the requirements for maintenance of the CMV-specific memory T-cell pool

Cytomegalovirus (CMV) infection promotes a broad T-cell response, with the resulting memory cells displaying diverse phenotypes. CMV establishes lifelong persistence/latency, and it is thought that viral antigens expressed during this period may regulate the expansion and/or maintenance of "inflationary" CD8 T-memory populations that display an effector memory phenotype. We show here that mouse CMV (MCMV)-specific inflationary memory T cells do not decrease in number after thymectomy, indicating that recent thymic emigrants are not strictly required for their maintenance. Furthermore, persistent MCMV replication in the salivary gland does not significantly impact the T-cell memory compartment, as surgical removal did not alter its composition. These results shed light upon the mechanisms required for maintenance of the large, MCMV-specific T-cell memory pool.

Primary response against cytomegalovirus during antiviral prophylaxis with valganciclovir, in solid organ transplant recipients

Antiviral prophylaxis has proved successful for prevention of cytomegalovirus (CMV) disease in solid organ transplant (SOT) patients; though emerging data suggest that antiviral agents interfere with immunity, and may inhibit immune priming. In this context, we investigated levels and phenotype of primary CMV-specific immune responses that developed during antiviral prophylaxis in a cohort of CMV seronegative recipients (R(-) ) of a SOT from a seropositive donor (D(+) ). We longitudinally monitored CMV viral load, antibodies and levels of the negative immuno-modulator IL-10. PBMC were stimulated with CMV-specific peptide libraries to measure CD137 activation marker on CMV-specific T-cells and levels of PD-1 receptor, which is over expressed on exhausted T-cells. Unexpectedly, the majority (13/18) of D(+) R(-) patients who developed a primary CMV response showed early post-transplant CMV-specific responses, though levels of PD-1 on CMV-specific T-cells remained elevated throughout prophylaxis. A strong inverse association was found between levels of plasma IL-10 and CMV-specific cellular immune responses. Our study suggests that during prophylaxis, subclinical CMV infection might have occurred in the D(+) R(-) patients, and primary CMV-specific responses were detected early post-transplant when levels of plasma IL-10 were low. Extended prophylaxis or antiviral treatment did not appear to suppress CMV-specific antibodies or T-cells, which, however, showed exhaustion phenotypes.

Understanding human T-cell-mediated immunoregulation through herpesviruses

Human herpesviruses have coevolved with humans over millions of years, and adaptation of latent infection within the cells of the immune system is a unique characteristic of many of these viruses. Following primary infection, these herpesviruses establish an asymptomatic-persistent infection in healthy individuals that is strictly controlled by virus-specific CD8(+) and CD4(+) T cells. Here, we provide a brief overview of how the human immune system interacts with these latent viruses and regulates the lifelong host-virus relationship in healthy virus carriers. Extensive studies on T-cell-mediated immune regulation over the last decade has allowed researchers to successfully translate these findings into the clinical setting to treat various herpesvirus-associated diseases in transplant patients and individuals with virus-associated malignancies. It is highly likely that these newly emerging T-cell-based therapeutic and diagnostic technologies will revolutionize the clinical management of patients with herpesvirus-associated diseases.

Immunotherapy and vaccination after transplant: the present, the future

Vaccination and adoptive immunotherapy for herpes virus infections has become an attractive option for the control of a virus family that negatively affects transplantation. In the future, enhanced ability to select antigen-specific T cells without significant in vitro manipulation should provide new opportunities for refining and enhancing adoptive immunotherapeutic approaches. This article focuses on advances in the area of vaccinology for some of these infections and in the use of adoptive immunotherapy. At present, many of these approaches in transplant recipients have focused on infections such as human cytomegalovirus, but the opportunity to use these examples as proof of concept for other infections is discussed.

Immunotherapy for persistent viral infections and associated disease

Persistent viral infections reflect a failure of the host's immune system to control infection, and in many cases, they are associated with the development of malignancies. So far, vaccines designed to boost viral immunity during chronic infection have not been successful. Infections with high-risk human papilloma viruses (e.g. HPV16) are acquired by a large segment of the population and persist in 5-10% of infected individuals, which causes the development of high-grade pre-malignant lesions. Recently we succeeded in causing regression of HPV16-induced disease in ∼50% of chronically infected patients by a novel therapeutic vaccine. Here, we summarize the parallels in immunity against HPV and other chronic viruses and discuss the general implications of our findings for the immunotherapy of chronic infections.

Current concepts on cytomegalovirus infection after liver transplantation

Cytomegalovirus (CMV) is the most common viral pathogen that negatively impacts on the outcome of liver transplantation. CMV cause febrile illness often accompanied by bone marrow suppression, and in some cases, invades tissues including the transplanted allograft. In addition, CMV has been significantly associated with an increased predisposition to allograft rejection, accelerated hepatitis C recurrence, and other opportunistic infections, as well as reduced overall patient and allograft survival. To negate the adverse effects of CMV on outcome, its prevention, whether through antiviral prophylaxis or preemptive therapy, is regarded as an essential component to the medical management of liver transplant patients. Two recent guidelines have suggested that antiviral prophylaxis or preemptive therapy are similarly effective in preventing CMV disease in modest-risk CMV-seropositive liver transplant recipients, while antiviral prophylaxis is the preferred strategy over preemptive therapy for the prevention of CMV disease in high-risk recipients [CMV-seronegative recipients of liver allografts from CMV-seropositive donors (D+/R-)]. However, antiviral prophylaxis has only delayed the onset of CMV disease in many CMV D+/R- liver transplant recipients, and at least in one study, such occurrence of late-onset primary CMV disease was significantly associated with increased mortality after liver transplantation. Therefore, optimized strategies for prevention are needed, and aggressive treatment of CMV infection and disease should be pursued. The standard treatment of CMV disease consists of intravenous ganciclovir or oral valganciclovir, and if feasible, one should also reduce the degree of immunosuppression. In one recent controlled clinical trial, valganciclovir was found to be as effective and safe as intravenous ganciclovir for the treatment of mild to moderate CMV disease in solid organ (including liver) transplant recipients. In this article, the authors review the current state and the future perspectives of prevention and treatment of CMV disease after liver transplantation.

Cytomegalovirus infection after liver transplantation incidence, risks, and benefits of prophylaxis

BACKGROUND

Cytomegalovirus (CMV) infection and related disease is a feared complication after liver transplantation. Antiviral prophylaxis is recommended in clinical practice guidelines depending on the CMV status of both donor and recipient as well as the individual risk profile.

METHODS

We retrospectively analyzed 211 liver transplant recipients with respect to the incidence of CMV infection after transplantation, the influence of donor and recipient CMV status, and the effect of antiviral prophylaxis. In addition, the underlying liver disease and immunosuppressive regimen were compared with the incidence of CMV infection. Patients were divided into 4 groups according to CMV donor/recipient (D/R) profile: group A (D-/R-) 28 patients (13.3%), group B (D-/R+) 64 patients (30.3%), group C (D+/R+) 79 patients (37.4%), and group D (D+/R-) 40 patients (19.0%).

RESULTS

CMV infection was observed in 17.9%, 29.7%, 24.1%, and 22.5% of the patients, respectively, with no significant difference in infection rates between the groups. CMV infection occurred in 5 patients (17.9%) in the presumed low-risk profile (group A), despite an antiviral prophylaxis in 4 out of these 5 patients. In contrast, CMV infection occurred in only 9/40 patients (22.5%) in the presumed high-risk profile (group D). The most frequent infection rates were found in groups B and C (R+ groups). After successful treatment of CMV infection, no recurrence was detected. Underlying liver disease or immunosuppressive protocol had no influence on CMV infection.

CONCLUSION

Approximately one fourth of patients will acquire CMV infection after liver transplantation independent of donor/recipient status. Surprisingly, antiviral prophylaxis does not seem to be sufficient to reduce this proportion of patients, either in presumed high-risk or in presumed low-risk situations.

Immunotherapy and vaccination after transplant: the present, the future

Vaccination and adoptive immunotherapy for herpes virus infections has become an attractive option for the control of a virus family that negatively affects transplantation. In the future, enhanced ability to select antigen-specific T cells without significant in vitro manipulation should provide new opportunities for refining and enhancing adoptive immunotherapeutic approaches. This article focuses on advances in the area of vaccinology for some of these infections and in the use of adoptive immunotherapy. At present, many of these approaches in transplant recipients have focused on infections such as human cytomegalovirus, but the opportunity to use these examples as proof of concept for other infections is discussed.

International consensus guidelines on the management of cytomegalovirus in solid organ transplantation

Cytomegalovirus (CMV) remains one of the most common infections after solid organ transplantation, resulting in significant morbidity, graft loss, and occasional mortality. Management of CMV varies considerably among transplant centers. A panel of experts on CMV and solid organ transplant was convened by The Infectious Diseases Section of The Transplantation Society to develop evidence and expert opinion-based consensus guidelines on CMV management including diagnostics, immunology, prevention, treatment, drug resistance, and pediatric issues.

Programmed death-1 receptor and interleukin-10 in liver transplant recipients at high risk for late cytomegalovirus disease

Despite significant advances in antiviral treatment, solid organ transplant (SOT) recipients remain at heightened risk for developing late cytomegalovirus (CMV) disease. Elevated inhibitory immune signaling suggests a state of immune impairment in SOT recipients, who do not control CMV infection and develop severe clinical symptoms after discontinuation of antiviral prophylaxis. We longitudinally monitored the negative immune modulator programmed death (PD)-1 receptor on both CD4 and CD8 T cells, co-expressing the CD137 surface marker of recent activation, in a liver transplant cohort. Liver recipients who progressed to CMV disease expressed elevated levels of PD-1 on CD137(+) CD4 and CD8 T cells, following stimulation with either full-length peptide libraries or CMV lysate. This novel approach, applicable to a multitude of human leukocyte antigen types, enhances the usefulness of the PD-1 measurements as a clinical strategy to predict late CMV disease. In parallel, we detected an increased level of the immunosuppressive cytokine interleukin (IL)-10, in plasma of liver recipients diagnosed with CMV disease. CMV-specific T cells were still functional when both PD-1 and IL-10 were upregulated; however they showed a marked proliferation deficit, which may limit their ability to contain viremia and lead to CMV disease. Our preliminary observations support further investigation of dual monitoring of PD-1 and IL-10, as potential immune markers of CMV disease.

CD4+ T cell help has an epitope-dependent impact on CD8+ T cell memory inflation during murine cytomegalovirus infection

Murine CMV (MCMV) establishes a systemic, low-level persistent infection resulting in the accumulation of CD8(+) T cells specific for a subset of viral epitopes, a process called memory inflation. Although replicating virus is rarely detected in chronically infected C57BL/6 mice, these inflationary cells display a phenotype suggestive of repeated Ag stimulation, and they remain functional. CD4(+) T cells have been implicated in maintaining the function and/or number of CD8(+) T cells in other chronic infections. Moreover, CD4(+) T cells are essential for complete control of MCMV. Thus, we wondered whether CD4(+) T cell deficiency would result in impaired MCMV-specific CD8(+) T cell responses. Here we show that CD4(+) T cell deficiency had an epitope-specific impact on CD8(+) T cell memory inflation. Of the three codominant T cell responses during chronic infection, only accumulation of the late-appearing IE3-specific CD8(+) T cells was substantially impaired in CD4(+) T cell-deficient mice. Moreover, the increased viral activity did not drive increased CD8(+) T cell division or substantial dysfunction in any MCMV-specific population that we studied. These data show that CD4(+) T cell help is needed for inflation of a response that develops only during chronic infection but is otherwise dispensable for the steady state maintenance and function of MCMV-specific CD8(+) T cells.

Increased programmed death-1 molecule expression in cytomegalovirus disease and acute graft-versus-host disease after allogeneic hematopoietic cell transplantation

To study the role of the programmed death-1 molecule (PD-1) in cytomegalovirus (CMV) infection and disease after allogeneic hematopoietic cell transplantation (HCT), 206 subjects were followed prospectively for immune response to CMV and assigned to 3 groups based on CMV outcome. The subjects were analyzed retrospectively for PD-1 expression in cryopreserved CD4+ and CD8+T cells collected at days 40, 90, 120, 150, 180, and 360 posttransplantation. HCT recipients with CMV disease (n=14) were compared with recipients with prolonged CMV infection, but no CMV disease (median duration of infection, 3 months; n=14) and with controls with no CMV infection who received similar transplants (n=22). The CMV disease group had a significantly higher mean fluorescein intensity of PD-1 in CD4+ (P < .05) and CD8+ (P < .05) lymphocytes at all time points studied. PD-1 expression also was significantly elevated in those with severe acute graft-versus-host disease (aGVHD), including the no-viremia group. The data suggest that PD-1 is induced by aGVHD even in the absence of CMV infection. This enhanced PD-1 expression during severe aGVHD and with CMV reactivation could explain the known role of aGVHD as a risk factor for CMV disease.